Nine gay couples sued the state of Maryland yesterday, contending that its ban on same-sex marriage is unconstitutional and should be overturned.

The couples filed the suit in Baltimore Circuit Court after officials in Baltimore and three counties, including Prince George's, denied them marriage licenses over the past two weeks. A gay man whose partner recently died, but who would like to marry one day, is also a plaintiff.

Attorneys for the American Civil Liberties Union, representing the plaintiffs, said they hope to make Maryland a test case in their ongoing struggle to legalize same-sex marriage.

Several other states, including California, New York, Washington and Oregon, face lawsuits challenging similar statutes. The actions follow a decision last fall by the Massachusetts Supreme Judicial Court that cleared the way for same-sex marriage in that state.

"We fully expect this case will end in the Maryland Court of Appeals, and that is where this case will be decided," said Kenneth Y. Choe, a lawyer for the ACLU's Lesbian & Gay Rights Project.

Maryland Attorney General J. Joseph Curran (D), whose office represents the county clerks who denied the licenses, said in a statement that he would defend the law. But Curran said it was "appropriate that the issue, which has been framed as a matter of civil rights, be decided by the courts."

Gov. Robert L. Ehrlich Jr. (R) characterized the suit as part of the ACLU's "far left agenda" and said he would support efforts in the General Assembly to clarify the law banning same-sex marriage. "Traditional marriage, in my view and the view of most Marylanders and Americans, is the cornerstone of our society," he said. "That used to be common sense."

The suit alleges that the Maryland law defining marriage as a union between a man and a woman violates the state constitution's equal protection clause. Same-sex couples are denied many of the rights accorded to married heterosexual couples, the plaintiffs say, including health care, certain tax benefits and the ability to make medical decisions for each other.

The nine couples, who include Patrick Wohahn, 28, and Dave Kolesar, 26, of College Park, sought marriage licenses in Baltimore or the counties of Prince George's, St Mary's and Dorchester.

"It just doesn't make sense that some families are at such a staggering disadvantage," said Lisa Polyak of Baltimore, who is a plaintiff along with her partner of 23 years.

Choe said he believes Maryland is fertile ground for a legal challenge because the state's courts have granted gay couples the right to adopt children and because the General Assembly approved a 2001 law protecting gay people from discrimination.

"Maryland courts have been increasingly recognizing gay and lesbian families deserve protection under the law," Choe said.

The lawsuit renewed calls from conservative lawmakers -- skeptical of Curran's resolve to fight the action -- for the General Assembly to approve legislation making it harder for the courts to overturn the statute.

In the spring, the House Judiciary Committee defeated a proposed constitutional amendment to outlaw same-sex marriage and another "defense of marriage" measure that would prohibit Maryland from recognizing such unions approved by other states.

"I think, unless we want our courts to be our policymaking body, that the legislature ought to set our policy and we ought to set it very, very clearly," said Del. Anthony J. O'Donnell (R-Calvert), the House minority whip.

But Senate President Thomas V. Mike Miller Jr. (D-Calvert) said he doubts the legislature will act on the issue in the near future because Marylanders have a "middle temperament."

Attorneys for the plaintiffs said Baltimore Circuit Court could rule on the matter by the end of the year. But they said it probably will be at least two years before appellate courts rule on the expected appeals.

Staff writer Christian Davenport contributed to this report.

Plaintiffs, from left, Gita Deane, Lisa Polyak, Charles Blackburn, Glen Dehn and Lisa Kebreau listen to Kenneth Y. Choe, an ACLU lawyer. Stacey Kargman-Kaye, left, and partner Jodi Kelber-Kaye walk to their car with their son after a news conference.